[jira] [Commented] (APEXCORE-577) Visitor API for DAG

["Pramod Immaneni (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/APEXCORE-577?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15729596#comment-15729596 ] 

Pramod Immaneni commented on APEXCORE-577:
------------------------------------------

Why specifically limit it to client side preparation of the DAG before the application is launched? Why not make it possible to have general hooks that can apply even when the application is running in the different distributed components of the application such as the containers and stram. The hooks could be registered to be asynchronous or synchronous. The asynchronous ones could be handled via a bus, we already have a bus called mbassador that we use today and it could potentially be used for this. The entire functionality is akin to something like dtrace without the dynamic part.

> Visitor API for DAG
> -------------------
>
>                 Key: APEXCORE-577
>                 URL: https://issues.apache.org/jira/browse/APEXCORE-577
>             Project: Apache Apex Core
>          Issue Type: Improvement
>            Reporter: Tushar Gosavi
>
> Support an Visitor like api for DAG, which could be used to write plugins for Apex.
> change DAG interface to add a visitor
> {code}
> registerVisitor(DagVisitor visitor)
> {code}
> The DagVisitor interface
> {code}
> interface DagVisitor {
>   boolean startDAG(DAG* dag);
>   boolean visitOperator(OperatorMeta *ometa)
>   boolean visitStream(StreamMeta *smeta);
>   boolean endDAG()
> }
> {code}
> dev thread discussions
> https://lists.apache.org/thread.html/1c37e0954cee029c9de537cc35ecb35beebdf49aba17de89bd2ce9ed@%3Cdev.apex.apache.org%3E



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